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Peat fuels representing four biomes of boreal (western Russia and Siberia), temperate (northern Alaska, USA), subtropical (northern and southern Florida, USA), and tropical (Borneo, Malaysia) regions were burned in a laboratory chamber to determine gas and particle emission factors (EFs). Tests with 25 % fuel moisture were conducted with predominant smoldering combustion conditions (average modified combustion efficiency (MCE) =0.82±0.08). Average fuel-based EF CO2 (carbon dioxide) are highest (1400 ± 38 g kg -1) and lowest (1073 ± 63 g kg -1) for the Alaskan and Russian peats, respectively. EF CO (carbon monoxide) and EF CH4 (methane) are ∼12 %–15 % and ∼0.3 %–0.9 % of EF CO2 , in the range of 157–171 and 3–10 g kg -1 , respectively. EFs for nitrogen species are at the same magnitude as EF CH4 , with an average of 5.6 ± 4.8 and 4.7 ± 3.1 g kg -1 for EF NH3 (ammonia) and EF HCN (hydrogen cyanide); 1.9±1.1 g kg -1 for EF NOx (nitrogen oxides); and 2.4±1.4 and 2.0 ± 0.7 g kg -1 for EF NOy (total reactive nitrogen) and EF N2O (nitrous oxide). An oxidation flow reactor (OFR) was used to simulate atmospheric aging times of ∼2 and ∼7 d to compare fresh (upstream) and aged (downstream) emissions. Filter-based EF PM2.5 varied by > 4-fold (14–61 g kg -1) without appreciable changes between fresh and aged emissions. The majority of EF PM2.5 consists of EF OC (organic carbon), with EF OC / EF PM2.5 ratios in the range of 52 %–98 % for fresh emissions and ∼14 %–23 % degradation after aging. Reductions of EF OC (∼7 –9 g kg -1) after aging are most apparent for boreal peats, with the largest degradation in low-temperature OC1 that evolves at < 140 ∘ C, indicating the loss of high-vapor-pressure semivolatile organic compounds upon aging. The highest EF Levoglucosan is found for Russian peat (∼16 g kg -1), with ∼35 %–50 % degradation after aging. EFs for water-soluble OC (EF WSOC) account for ∼20 %–62 % of fresh EF OC. The majority (> 95 %) of the total emitted carbon is in the gas phase, with 54 %–75 % CO2 , followed by 8 %–30 % CO. Nitrogen in the measured species explains 24 %–52 % of the consumed fuel nitrogen, with an average of 35 ± 11 %, consistent with past studies that report ∼1/3 to 2/3 of the fuel nitrogen measured in biomass smoke. The majority (> 99 %) of the total emitted nitrogen is in the gas phase, with an average of 16.7 % as NH3 and 9.5 % as HCN. N2O and NOy constituted 5.7 % and 2.9 % of consumed fuel nitrogen. EFs from this study can be used to refine current emission inventories. [ABSTRACT FROM AUTHOR]

Smoke from laboratory chamber burning of peat fuels from Russia, Siberia, the USA (Alaska and Florida), and Malaysia representing boreal, temperate, subtropical, and tropical regions was sampled before and after passing through a potential-aerosol-mass oxidation flow reactor (PAM-OFR) to simulate intermediately aged (∼2 d) and well-aged (∼7 d) source profiles. Species abundances in PM2.5 between aged and fresh profiles varied by several orders of magnitude with two distinguishable clusters, centered around 0.1 % for reactive and ionic species and centered around 10 % for carbon. Organic carbon (OC) accounted for 58 %–85 % of PM2.5 mass in fresh profiles with low elemental carbon (EC) abundances (0.67 %–4.4 %). OC abundances decreased by 20 %–33 % for well-aged profiles, with reductions of 3 %–14 % for the volatile OC fractions (e.g., OC1 and OC2, thermally evolved at 140 and 280 ∘ C). Ratios of organic matter (OM) to OC abundances increased by 12 %–19 % from intermediately aged to well-aged smoke. Ratios of ammonia (NH 3) to PM2.5 decreased after intermediate aging. Well-aged NH4+ and NO3- abundances increased to 7 %–8 % of PM2.5 mass, associated with decreases in NH3 , low-temperature OC, and levoglucosan abundances for Siberia, Alaska, and Everglades (Florida) peats. Elevated levoglucosan was found for Russian peats, accounting for 35 %–39 % and 20 %–25 % of PM2.5 mass for fresh and aged profiles, respectively. The water-soluble organic carbon (WSOC) fractions of PM2.5 were over 2-fold higher in fresh Russian peat (37.0±2.7 %) than in Malaysian (14.6±0.9 %) peat. While Russian peat OC emissions were largely water-soluble, Malaysian peat emissions were mostly water-insoluble, with WSOC / OC ratios of 0.59–0.71 and 0.18–0.40, respectively. This study shows significant differences between fresh and aged peat combustion profiles among the four biomes that can be used to establish speciated emission inventories for atmospheric modeling and receptor model source apportionment. A sufficient aging time (∼7 d) is needed to allow gas-to-particle partitioning of semi-volatilized species, gas-phase oxidation, and particle volatilization to achieve representative source profiles for regional-scale source apportionment. [ABSTRACT FROM AUTHOR]